Oral Administration of Bovine and Porcine Milk Exosome Alter miRNAs Profiles in Piglet Serum.

Breast milk is the most important nutrient source for newborn mammals. Studies have reported that milk contains microRNAs (miRNAs), which are potential regulatory components. Currently, existing functional and nutritional two competing hypotheses in milk field though little date have been provided for nutritional hypothesis. In this study, we used the qRT-PCR method to evaluated whether milk miRNAs can be absorbed by newborn piglets by feeding them porcine or bovine milk. The result showed that miRNA levels (miR-2284×, 2291, 7134, 1343, 500, 223) were significantly different between bovine and porcine milk. Four miRNAs (miR-2284×, 2291, 7134, 1343) were significantly different in piglet serum after feeding porcine or bovine milk. After separated milk exosomes by ultracentrifugation, the results showed the selected milk miRNAs (miR-2284×, 2291, 7134, 1343) were present in both exosomes and supernatants, and the miRNAs showed the coincidental expression in IPEC-J2 cells. All our founding suggested that the milk miRNAs can be absorbed both in vivo and in vitro, which will building the foundation for understanding whether these sort of miRNAs exert physiological functions after being absorbed and provided additional evidence for the nutritional hypotheses.

In low protein diets, microRNA-19b regulates urea synthesis by targeting SIRT5.

Ammonia detoxification, which takes place via the hepatic urea cycle, is essential for nitrogen homeostasis and physiological well-being. It has been reported that a reduction in dietary protein reduces urea nitrogen. MicroRNAs (miRNAs) are major regulatory non-coding RNAs that have significant effects on several metabolic pathways; however, little is known on whether miRNAs regulate hepatic urea synthesis. The objective of this study was to assess the miRNA expression profile in a low protein diet and identify miRNAs involved in the regulation of the hepatic urea cycle using a porcine model. Weaned 28-days old piglets were fed a corn-soybean normal protein diet (NP) or a corn-soybean low protein diet (LP) for 30 d. Hepatic and blood samples were collected, and the miRNA expression profile was assessed by sequencing and qRT-PCR. Furthermore, we evaluated the possible role of miR-19b in urea synthesis regulation. There were 25 differentially expressed miRNAs between the NP and LP groups. Six of these miRNAs were predicted to be involved in urea cycle metabolism. MiR-19b negatively regulated urea synthesis by targeting SIRT5, which is a positive regulator of CPS1, the rate limiting enzyme in the urea cycle. Our study presented a novel explanation of ureagenesis regulation by miRNAs.